Referring to 55-year-old Walter James Palmer as a “foreign poacher,” Oppah Muchinguri told a news conference that the prosecutor general had started the process to have him extradited from the United States.

“We are appealing to the responsible authorities for his extradition to Zimbabwe so that he can be held accountable for his illegal action,” she said.

Palmer has admitted killing the 13-year-old predator, a favorite with foreign tourists and the subject of an Oxford University study, but said he had hired professional guides and believed all the necessary hunting permits were in order.

Muchinguri also said Palmer’s use of a bow and arrow to kill the lion, who is said to have been lured out of Hwange National Park with bait before being shot, was in contravention of Zimbabwean hunting regulations.

Palmer, a life-long big game hunter from Minnesota, managed to return to the U.S. before the authorities were aware of the controversy around Cecil’s death.

“It was too late to apprehend the foreign poacher because he had already absconded to his country of origin,” Muchinguri said.

The killing has sparked social media outrage against Palmer in the United States. The White House said on Thursday it would review a public petition of more than 100,000 signatures to have him extradited.